The present invention relates in general to fish counters.
Scientists monitor the movement of aquatic animals for various reasons, including the determination of environmental influences on upstream migration. Fish counters are often used to monitor animal movement and may be positioned at fishways on dams to count the number of fish passing through the fishways. Additional data often needed to manage populations of certain types of fish, such as the American eel, include the date and time of passage of each individual through an area, identification of the species of animal passing through an area, and estimates of body length/size of all individuals passing through an area.
However, periods of turbid (i.e., muddy) water conditions can interfere with the collection of data. Water turbidity limits the ability to observe fish underwater in their natural environment. Trapping fish is labor-intensive and may interfere with the behavior of the fish. Remotely-operated electronic monitoring devices, while overcoming the limitations of manual trapping, are still adversely affected by water turbidity. For example, the beams emitted from optical scanners that use infrared light may attenuate and not be detected, impairing the functioning of the scanner and interfering with achieving an accurate count of the number of fish passing through an area. Also, photographs taken in turbid water may not be clear, which interferes with identification of the animals and estimates of body size.
Thus, a need exists for an improved fish monitoring device that monitors aquatic animals such as the American eel without being limited by water turbidity.